With increasing of electronic industries, the electronic devices are developed toward minimization, high operating speed and increasing integration level. Due to the reduced size, many electronic components are packaged in a stacked form. Take a capacitor for example. For increasing the capacitance and reducing the layout area of the capacitor on the circuit board, a stacked capacitor was developed.
Referring to FIG. 1, a schematic cross-sectional view of a conventional stacked capacitor is illustrated. The stacked capacitor 1 is disposed on a circuit board 2 and includes two energy storage units 10. Each energy storage unit 10 includes a first electrode 101 and a second electrode 102 at bilateral sides thereof. The stacked capacitor 1 further includes a first metallic terminal 11 and a second metallic terminal 12. The first electrodes 101 of these two energy storage units 10 are bonded to the first metallic terminal 11 via a soldering material 13 such that these two first electrodes 101 are electrically connected to each other. Similarly, the second electrodes 102 of these two energy storage units 10 are bonded to the second metallic terminal 12 via the soldering material 13 such that these two second electrodes 102 are electrically connected to each other. The bottom surfaces of the first metallic terminal 11 and the second metallic terminal 12 are fixed on the circuit board 2 via a soldering material 14 according to a surface mount technology. Accordingly, the first electrodes 101 and the second electrodes 102 of the energy storage units 10 are electrically connected to the circuit board 2 through the first metallic terminal 11 and the second metallic terminal 12.
During the process of welding the first electrodes 101 and the second electrodes 102 of these two energy storage units 10 to the first metallic terminal 11 and the second metallic terminal 12, the first electrodes 101 need to be precisely aligned with the first metallic terminal 11 and/or the second electrodes 102 need to be precisely aligned with the second metallic terminal 12. If the alignment is not proper, the amount of the soldering material 13 is insufficient and thus the solderability of the soldering material 13 is unacceptable. Under this circumstance, the first metallic terminal 11 and the second metallic terminal 12 fail to be firmly bonded to the energy storage units 10. In addition, since the stacked capacitor 1 is mounted on the circuit board 2 via the soldering material 14 according to a surface mount technology, the soldering material 13 between the first electrodes 101 and the first metallic terminal 11 and/or the soldering material 13 between the second electrodes 102 and the second metallic terminal 12 may be molten during the reflowing process. Therefore, the energy storage units 10 are not electrically connected to the first metallic terminal 11 and/or the second metallic terminal 12.
During operation, the stacked capacitor 1 may generate energy in the form of heat, which is readily accumulated and difficult to dissipate away. Under this circumstance, the circuit board 2 is readily suffered from thermal expansion. Due to a thermal expansion coefficient difference between the stacked capacitor 1 and the circuit board 2, the energy storage units 10 are possibly cracked. Since the structure of the stacked capacitor 1 is damaged, the stacked capacitor 1 fails to operate normally.
In views of the above-described disadvantages resulted from the conventional method, the applicant keeps on carving unflaggingly to develop an electronic component and a fastening device thereof according to the present invention through wholehearted experience and research.